Nanaomycin B and therapeutic compositions containing same

ABSTRACT

The present invention relates to new compound designated as nanaomycin B represented by general formula: ##STR1## Nanaomycin B is a quinone type and is active on mycoplasma, Gram-positive bacteria and trycophyton. This compound is useful as a medicament for infectious diseases of humans and animals caused by a parasite of trichophyton or mycoplasma etc. The acute toxicity (LD 50 , intra-penetrial injection) in mice of this compound is 169 mg/Kg. 
     Nanaomycin B is produced by fermentation in which a nanaomycin-producing strain belonging to the genus Streptomyces is cultured in a medium under aerobic conditions and the accumulated nanaomycin B in the cultured broths is recovered therefrom.

RELATED APPLICATION

This is a division of Application Ser. No. 358,216 filed Dec. 7, 1977 now U.S. Pat. No. 4,194,064 which is a continuation of Ser. No. 719,752 filed Sept. 2, 1976 which is a continuation-in-part of Ser. No. 558,514 filed Mar. 14, 1975.

SUMMARY OF THE INVENTION

The present invention relates to new compound designated as nanomycin B as well as to a process for producing the same by fermentation.

Nanaomycin B is also designated as OS-3966-B or Rosanomycin B and represented by general formula: ##STR2##

The above-mentioned formula has been determined by various experiments including nuclear magnetic resonance spectra, elementary analysis, mass-spectra and the like.

DRAWINGS

FIGS. 1 and 2 show UV and IR absorption spectra of nanaomycin B, respectively.

Nanaomycin B is in the form of pale-yellow powder and has the following physical and chemical characteristics:

1. Elementary analysis: Found: C-59.70%; H-4.90%; N-0%: Calculated (as C₁₆ H₁₆ O₇): C-59.99%; H-5.03%; N-0%.

2. Molecular weight: m/e determined by mass spectrum is 320.090 and the theoretical value of m/e for C₁₆ H₁₆ O₇ is 320.090.

3. Melting point: About 84°-86° C.

4. Specific rotation: [ ]_(D) ²⁶ -74.5° (C-1.0, methanol)

5. Ultraviolet absorption spectrum (FIG. 1): _(max) ^(MeOH) nm (): 231 (2.08×10⁴), 248 (shoulder) (0.870×10⁴), 269 (shoulder) (0.503×10⁴), 352 (0.497×10⁴)

6. Infrared absorption spectrum (FIG. 2): Specific, comparatively strong absorptions at 3500-2900, 1705, 1648, 1605, 1450, 1380, 1355, 1268, 1210-1240, 1160 and 1107 cm⁻¹ (by KBr method)

7. Solubility: Easily soluble in methanol, ethanol, ethylacetate, chloroform, acetone and ether. Insoluble in n-hexane, petroleum ether and water.

8. Color reaction: Positive in the reactions with ferric chloride and reduction catalyst [Feigl, N., Anal. Chem., 28, 397 (1956)]. Negative in ninhydrin reaction, Sakaguchi reaction, Ehrlich reaction, Fehling reaction and Molish reaction.

As is apparent from the foregoing characteristics, nanaomycin B is considered to be a quinone type compound which is, however, not identified with any known compounds. Accordingly, it has been confirmed that nanaomycin B is a new compound.

The antimicrobial spectra of nanaomycin B is shown in Table 1.

As is apparent from the foregoing characteristics, nanaomycin B is considered to be a quinone type compound which is however not identified with any known compounds. Accordingly, it has been confirmed that nanaomycin B is a new compound.

The antimicrobial spectra of nanaomycin B is shown in Table 1.

                  TABLE 1                                                          ______________________________________                                         Test organisms       Medium   MIC (μg/ml)                                   ______________________________________                                         Bacillus subtillis PCI 219                                                                          N        7.8                                              Staphylococcus aureus FDA 209P                                                                      N        3.9                                              Staphylococcus aureus FDA 209P (JC-1)                                                               N        2.0                                              Sarcina lutea PCI 1001                                                                              N        2.0                                              Mycobacterium smegmatis                                                                             N        125                                              Escherichia coli NIHJ                                                                               N        15.6                                             Escherichia coli NIHJ (JC-2)                                                                        N        500                                              Klebsiella pneumoniae PCI 602                                                                       N        31.3                                             Salmonella typhimurium                                                                              N        62.5                                             Shigella flexneri    N        62.5                                             Xanthomonas oryzae N-5824                                                                           N        125                                              Pseudomonas aeruginosa                                                                              N        >500                                             Candida albicans     P        31.2                                             Saccharomyces sake   P        62.5                                             Aspergillus niger ATCC 6275                                                                         P        62.5                                             Aspergillus fumigatus IAM 2612                                                                      P        >100                                             Piricularia oryzae   P        15.6                                             Microsporum gypseum 704                                                                             P        12.5                                             Trichophyton asteroides                                                                             P        12.5                                             Trichophyton ferrugineum                                                                            P        12.5                                             Trichophyton interdigitale                                                                          P        12.5                                             Trichophyton mentagrophytes                                                                         P        25                                               Trichophyton pedis 804                                                                              P        3.1                                              Trichophyton purpureum                                                                              P        25                                               Trichophyton roseum  P        12.5                                             Trichophyton rubrum  P        3.1                                              Trichophyton schoenleini                                                                            P        3.1                                              Trichophyton violaceum                                                                              P        3.1                                              Mycoplasma gallisepticum KP-13                                                                      H        <0.013                                                                E        0.10                                             Mycoplasma gallisepticum S-6                                                                        H        <0.013                                                                E        0.10                                             Mycoplasma gallisepticum 333P                                                                       H        0.013                                            (Spiramycin resistant)                                                                              E        0.05                                             Mycoplasma gallinarum                                                                               H        3.12                                             Mycoplasma iners     H        3.12                                             Mycoplasma pneumonia E        0.05                                             Acholeplasma laidlawii (A) PG8                                                                      H        >25                                                                   E        >25                                              Acholeplasma laidlawii (B) Bml                                                                      H        25                                                                    E        >25                                              ______________________________________                                          Note:                                                                          Medium N  nutrient agar (pH 7.0, 2 days, 37° C.)                        P  potato agar (pH 6.4, 4 days, 27° C.)                                 H  Hokken PPLO agar (pH 7.8, 8 days, 37° C.)                            E  Eiken PPLO agar (pH 7.8, 8 days, 37° C.)                             MIC  Minimal inhibitory concentration                                    

As is shown in Table 1, nanaomycin B has a high activity against mycoplasma. For example, the growth of Mycoplasma gallisepticum is inhibited by nanaomycin B at a concentration of not more than 0.1 μg/ml. A high antimicrobial activity on nanaomycin B on a spiramycin-resistant Mycoplasma gallisepticum is observed. Also, nanaomycin B inhibits the growth of Gram-positive bacteria such as, for example Staphylococcus aureus at a concentration of 2.0 to 8.0 μg/ml and the growth of various fungi of some species belonging to the genus Trichophyton at a concentration of not more than 25.0 μg/ml.

An excellent therapeutic effect is exhibited by nanaomycin B on various infectious diseases caused by a parasite of the genus Tricophyton in the body of animals. When dermatomycosis caused by Tricophyton metagrophytes at the back of guinea pigs is treated by applying a solution of 0.01-1% nanomycin B dissolved in propylene glycol-ethanol (3:1, v/v) once daily for 8 days, an excellent therapeutic effect on erythema and scales is observed. Nanaomycin B has furthermore a therapeutic effect on various diseases of humans and animals, and its therapeutic effect on a chronic respiratory disease of chickens caused by Mycoplasma gallisepticum is observed.

When dermatomycosis of cattle caused by mass infection of Trichophyton verrucosum is treated with nanaomycin B, nanaomycin B is dissolved or suspended in a suitable carrier, for example, olive oil, and is coated on the affected part directly with or without removal of the scales. SP-Burton, a commercial product available from Rakuno-shinko K.K., Japan, which is considered as a most effective agent for dermatomycosis of animals, is used as a control therapeutic agent. The therapeutic effects are observed for four weeks. The results obtained by coating nanaomycin B once and by twice coatings (the second coating is carried out a week after the first coating) are shown in tables 2 and 3, respectively.

                  TABLE 2                                                          ______________________________________                                                        Result                                                                          AFTER                                                                    Con.    Sam-   1     2     3     4                                   Agent     mg/ml   ple    week  weeks weeks weeks                               ______________________________________                                         I   Nanaomycin                                                                               0.1     1     ++    ++   +++   +++                                   B                                                                              Nan-      1       1    +++   +++   +++   +++                                   aomycin B                                                                      Nan-      10      1    +++   +++   +++   +++                                   aomycin B                                                                      SP-Burton 0.3     1    -     -     -     -                                 II  Nanaomycin                                                                               0.1     1    +++   +++   +++   +++                                   B                                                                              Nan-      1       1    +++   +++   +++   +++                                   aomycin B                                                                      Nan-      10      1    +++   +++   +++   +++                                   aomycin B                                                                      SP-Burton 0.3     1    +++   +     -     -                                 ______________________________________                                          Note:                                                                           I  direct coating on affected part                                            II  coating after removing the scales of affected part                         Con.  concentration of agent                                                   +++ complete removal of scales and recovered                                   ++ a little scales remained                                                    + removal of a part of scales                                                  - no removal of scale and no recovery                                    

                  TABLE 3                                                          ______________________________________                                                        Result                                                                         AFTER                                                                     Con.    Sam-   1     2     3     4                                   Agent     mg/ml   ple    week  weeks weeks weeks                               ______________________________________                                         I   Nan-                                                                           aomycin B 0.1     1    ++    +++   +++   +++                                   Nan-                                                                           aomycin B 1       1    ++    ++    +++   +++                                   Nan-                                                                           aomycin B 10      1    +++   +++   +++   +++                                   SP-Burton 0.3     1    -     -     -     -                                 II  Nan-                                                                           aomycin B 0.1     1    +++   +++   +++   +++                                   Nan-                                                                           aomycin B 1       1    +++   +++   +++   +++                                   Nan-                                                                           aomycin B 10      1    +++   +++   +++   +++                                   SP-Burton 0.3     1    +++   ++    +     -                                 ______________________________________                                          Note:                                                                          I  direct coating on affected part                                             II  coating after removing the scales of affected part                         Con.  concentration of agent                                                   +++ complete removal of scales and recovered                                   ++ a little scales remained                                                    + removal of a part of scales                                                  - no removal of scale and no recovery                                    

The antifungal activity of nanaomycin B is shown in Table 4, in which the antifungal activity of nanaomycin B is superior to that of the known antibiotic ethylkalafunginate (ethylkalamycinate) though slightly inferior to that of the known compound of deoxyfrenolicin. Nanaomycin B exhibits stronger antifungal activity when the pH of the medium is higher than 6.4 shown in Table 4.

                  TABLE 4                                                          ______________________________________                                         Antifungal Activity                                                                           Minimal Inhibitory Con. (μg/ml)                                               Nan-                                                          Test Organisms   aomycin B Y         Z                                         ______________________________________                                         Candida albicans >100      50        >100                                      Saccharomyces sake                                                                              >100      6.3       >100                                      Aspergillus fumigatus                                                                           50        6.3       >100                                      Aspergillus niger                                                                               >100      >100      >100                                      Microsporum gypseum                                                                             12.5      <0.2      >100                                      Trichophyton asteroides                                                                         12.5      <0.2      >100                                      Trichophyton ferrugineum                                                                        6.3       3.1       >100                                      Trichophyton interdigitale                                                                      12.5      0.4       >100                                      Trichophyton rubrum                                                                             6.3       <0.2      >100                                      Trichophyton schoenleini                                                                        0.4       <0.2      >100                                      Trichophyton violaceum                                                                          6.3       0.8       >100                                      ______________________________________                                          Note:                                                                          Minimal inhibitory concentration is assayed by agar dilution method            (potato agar, pH 6.4, 27° C., 4 days)                                   Y  deoxyfrenolicin                                                             Z  ethylkalafunginate (ethylkalamycinate)                                

Table 5 shows the antimycoplasma activity of nanaomycin B, which is superior to those of ethylkalafunginate and deoxyfrenolicin.

                  TABLE 5                                                          ______________________________________                                         Antimycoplasma Activity                                                                      Concentration  Inhibitory                                        Antibiotic    (μg/ml)     Zone (mm)                                         ______________________________________                                         Nanaomycin B  10             22.7                                                            100            32.6                                              Deoxyfrenolicin                                                                              10             14.6                                                            100            21.8                                              Ethylkalfunginate                                                                            10             none                                                            100            none                                              ______________________________________                                          Note:                                                                          Inhibitory zone is assayed by paper disc method (Eiken PPLO agar, pH 7.8,      37° C., 1 day).                                                   

As apparent from the above tables, nanaomycin B exhibits an especially strong activity on mycoplasma, and is also active on Gram-positive bacteria and trycophyton. Accordingly, it can be said that nanaomycin B represents a new antibiotic which may be used as a medicament for human beings and animals. LD₅₀ of nanaomycin B (determined by intra-penetrial injection into mouse) is 169 mg/Kg.

According to another aspect of the present invention, there is provided a process for producing nanaomycin B, characterized by the fact that a microorganism which belongs to the genus Streptomyces and which is capable of producing nanaomycin B is cultured aerobically in a medium to accumulate nanaomycin B in the cultured broths and the accumulated nanaomycin B is then recovered therefrom.

For the purpose of the present invention, it is possible to use not only the hereinafter described Streptomyces rosa var. notoensis and any mutant obtained therefrom but also any strain which belongs to the genus Streptomyces and which is capable of producing nanaomycin B. The microbiological characteristics of a preferable strain Streptomyces rosa var. notoensis which is used in the following examples to produce nanaomycin B are as follows:

1. Morphological characteristics:

Forming abundantly aerial mycelium on both synthetic and natural agar media, the ending of which forming massy or irregular spiral. Conidiophore formed on aerial mycelium. Coridiospores are oval (0.6-1.0μ) and in a chain of 10 or more. The spores have smooth surfaces.

2. Cultural characteristics:

Shown in Table 6.

                                      TABLE 6                                      __________________________________________________________________________     Cultural Characteristics of S. rose var. notoensis(FERM 2209)                  Medium     Growth      Reverse   Aerial mycelium                                                                          Soluble pigment                     __________________________________________________________________________     Sucrose-nitrate                                                                           good, light ivory to                                                                       light melon yellow                                                                       light apricot                                                                            pearl pink to                       agar       light melon yellow                                                                         to apricot          light melon yellow                  Glucose-nitrate                                                                           good, dusty yellow                                                                         golden brown to                                                                          white to pearl pink                                                                      light wheat to                      agar       to golden brown                                                                            chocolate brown     sepia brown                         Glycerol-asparagine                                                                       good, light melon                                                                          apricot   light apricot                                                                            melon yellow to                     agar       yellow to orange rust           apricot                             Inorganic salt-                                                                           moderate    pearl pink to                                                                            white to flesh                                                                           dark luggage tan                    starch agar                                                                               light melon yellow                                                                         golden brown                                                                             pink      to sepia brown                      Tyrosine agar                                                                             good, light wheat to                                                                       light melon yellow                                                                       light melon yellow                                                                       light wheat to                                 amber topaz to nude tan                                                                              to pearl pink                                                                            melon yellow                        Nutrient agar                                                                             moderate, colorless                                                                        squash yellow to                                                                         white, scant                                                                             none                                           to pearl pink                                                                              bright yellow                                           Glucose-peptone                                                                           moderate, colorless                                                                        golden brown to                                                                          white     ivy to dark                         agar       to golden brown                                                                            sepia brown         laurel                              Yeast extract-salt                                                                        good, colorless to                                                                         golden brown to                                                                          light melon yellow                                                                       ivy                                 extract agar                                                                              golden brown                                                                               orange rust                                                                              to light apricot                              Oatmeal agar                                                                              moderate, colorless                                                                        light melon yellow                                                                       light melon yellow                                                                       light tan                                      to light melon yellow                                                                      to nude tan                                                                              to light apricot                              Peptone-yeast extract                                                                     moderate, cream to                                                                         colonial yellow                                                                          scant, white to                                                                          none                                iron agar  light wheat           colonial yellow                               Tryptone-yeast                                                                            surface rowth,                                                                             light ivory                                                                              white     none                                extract broth                                                                             moderate, light ivory                                               Milk       pearl pink            none      light apricot to                                                               pearl pink                          Gelatin    surface growth, good                                                                       pearl pink to                                                                            white to celadon                                                                         laurel                                                     chartreuse tint                                                                          gray                                          Nitrate broth                                                                             surface growth,                                                                            light ivory                                                                              white     none                                           moderate                                                            Cellulose  none        none      none      none                                __________________________________________________________________________

3. Physiological characteristics:

Growth temperature: 15°-45° C.

Liquefaction of gelatin: positive

Hydrolyzation of starch: positive

Coagulation of skim milk: positive

Peptonization of skim milk: positive

Formation of melanoid pigment: negative

Formation of tyrosinase: negative

Reduction of nitrate: positive

Formation of hydrogen sulfide: negative

Decomposition of cellulose: negative

4. Usability of various carbon sources:

Arabinose, xylose, glucose, fructose, rhamnose, mannitol, glycerol, maltose and mannose may be usable; while sucrose, innositol and raffinose may be unusable.

The microbiological characteristics of this strain are summarized as follows:

Conidiophore is spiral and conidiospore is smooth. Growth on synthetic medium is colored in yellowish gray or orange gray or reddish brown, and the formed aerial mycelium is colored in white or orange gray or pink. There is formed a soluble pigment colored in yellowish brown or dark reddish brown. When an organic medium is used, the growth is generally colorless or colored in orange gray or brown, and the formed mycelium is colored in white or orange gray or pink. Sometimes soluble pigment is not formed, while a greenish gray or grayish black pigment is formed in some media. This strain is non-chromogenic and has a relatively high activity with regard to the decomposition of protein and starch.

With respect to the strains having the aforementioned characteristics, a search was made for strains having analogous characteristics to those of the strain used in the following examples with reference, for example, to "The Actinomycetes" by S. A. Waksman, Vol. 2 (1961) and "Cooperative Description of Type Strains of Streptomyces" by E. B. Shirling and D. Gottlieb [International Journal of Systematic Bacteriology, Vol. 18, No. 2, pages 69-189 (1968); Vol. 18, No. 4, pages 279-392 (1969); Vol. 9, No. 4, pages 391-512 (1969); and Vol. 22, No. 4, pages 265-394 (1972)]. As a result, some species designated as "fradiae", i.e. Streptomyces fradiae, Streptomyces luridus, Streptomyces roseus, Streptomyces fuscus, Streptomyces roseoluteus, and Streptomyces rosa were found as being analogous. Among them, Streptomyces roseoluteus and Streptomyces rosa are indeed likely to be most analogous. However, on one hand Streptomyces roseoluteous is distinguishable from the nanaomycin-producing strain of the present invention because the color at the reverse side of S. roseoluteus's colony becomes yellowish orange from yellow in certain media such as for example of yeast extract-malt extract, oat meal agar, inorganic starch agar as well as of glycerol-asparagine agar, with simultaneously formation of yellowish soluble pigment. On the other hand, Streptomyces rosa is generally similar to the nanaomycin-producing strain according to the present invention with the exception that the production of soluble pigment in a certain media such as for example of yeast extract-malt extract agar, glucose-peptone agar and that the reduction of nitrate is not observed in the case of Streptomyces rosa. Accordingly, this strain is designated as Streptomyces rosa var. notoensis.

The nanaomycin-producing strain used in the following examples produces simultaneously in the cultured broths nanaomycin B and nanaomycins A and C represented by general formulae: ##STR3## and referred to in the related U.S. patent application entitled "New Antibiotic Nanaomycin A and its related compounds" and filed concurrently with this application.

The strain used in the following examples has been deposited on an unrestricted basis with the Fermentation Research Institute, Agency of Industrial Science and Technology, Japanese Government, and assigned an accession number of FERM-P No. 2209.

According to the process of the present invention, either any synthetic or organic medium may be used when it contains a suitable carbon source, nitrogen source, inorganic substances and, if desired, various other nutrients. Various carbon and nitrogen sources may be used when these sources are adaptable for the strain in use.

More concretely, the useful carbon sources are exemplified by various carbohydrates such as glucose, glycerol, fructose, maltose, mannitol, xylose, galactose, lactose, ribose, starch and starch hydrolyzate. The concentration of carbon source is preferably 0.5-5.0% (when calculated as glucose) based upon the medium. It is also possible to use organic acids such as, for example, gluconic acid, pyruvic acid, lactic acid, acetic acid; and various amino acids such as glycine, glutamic acid, alanine, etc.

As the nitrogen source, it is possible to use, for example, ammonia; various inorganic and organic ammonium salts such as ammonium chloride, ammonium phosphate, ammonium sulfate, ammonium nitrate; nitrogen-containing organic materials such as urea, peptone, NZ-amine, meat extract, dried yeast, yeast extract, corn steep liquor, casein hydrolyzate, fish meal, digested product thereof, soybean meal, digested products thereof, defatted soybean, digested products thereof, pupa hydrolyzate, and various amino acids such as glycine, glutamic acid, alanine, etc.

As the inorganic substance, it is possible to use, for example, various phosphates, magnesium sulfate, etc. If desired, it is also possible to use a trace amount of heavy metal salts, which is however, not always essential when the medium used contains natural materials. In case a mutant strain having a nutritional requirement is used, it is necessary to add the required substance to the medium.

Liquid medium is preferable for producing large amount of nanaomycins A, B and C, though solid medium may be used. It is possible to use a seed medium having a similar composition to that of the main culture medium, and the seed is preferably obtained by fermentation carried out aerobically at a temperature of 27° C. for two days, for example, by using a Sakaguchi flask.

The fermentation is carried out aerobically with shaking and/or submerged conditions at a temperature of from 15° to 40° C. at an adjusted pH of 6-10 for about 2-8 days, whereby large amounts of nanaomycins A, B and C are accumulated concurrently in the medium and microbial body. After completion of the fermentation, nanaomycins A, B and C are recovered from the cultured broths. For example, the broths are separated into the microbial body and filtrate. The filtrate is adjusted to an acidic pH (preferably from 2 to 4) with HCl or the like and is then subjected to extraction with a suitable organic solvent such as e.g. ethyl acetate or butyl acetate. After this, nanaomycins A, B and C are obtained by purifying the extracted substance in a conventional manner which would be used for the purification of known substances soluble in organic solvents.

According to the present invention, preferable methods for the fermentation are examplified as follows:

A culture medium (100 ml) is put in a 500 ml Sakaguchi flask and sterilized at a temperature of 120° C. for 15 minutes. After this, spores and/or mycelium of the used strain are inoculated and the fermentation is effected with shaking (110 r.p.m.) at a temperature of 27° C. for a sufficient period of time (e.g. for 3 days) to accumulate large amounts of nanaomycins A, B and C in the culture broths.

Alternatively, a culture medium (20 liters) is put into a 30-liter jar fermentor and sterilized at a temperature of 120° C. for 15 minutes. After this, a seed culture is inoculated and the fermentation is effected at a temperature of 27° C. for three days with shaking (300 r.p.m.) and aeration (10 l/min). It is also preferred to culture using a medium (200 ml) in a tank-type fermentor (capacity-400 liters) for three days at 27° C. with shaking (200 r.p.m.) and aeration (100 l/min).

In either case, good results can be obtained by using glycerin and soybean meal as the carbon and nitrogen sources, respectively. A medium containing glycerine (2.0%), soybean meal (2.0%) and NaCl (0.3%) and having a pH of 7.0 is particularly advantageous. In one embodiment using this medium, an inhibition zone (diameter-30 cm) is observed in the supernatant of the cultured liquor at a pH of 5.2 after culturing at a temperature of 27° C. for 70 hours by using a tank-type fermentor. Although nanaomycins A, B and C are found in both the fermented liquid and solid materials, the former contains usually larger amounts of nanaomycins A, B and C than the latter.

After completion of the fermentation, nanaomycins A, B and C are recovered from the cultured broths in the following manner:

The cultured broths are separated into solid and liquid phases in conventional manner by means of filtering, centrifuging and the like. The liquid phase, i.e. the filtrate is adjusted to an acidic pH (preferably from 2 to 4) with HCl or the like, and is then subjected to extraction with a suitable organic solvent such as e.g. ethyl acetate or butyl acetate. After this, nanaomycins A and B are obtained by purifying the extracted substance in a conventional manner which is applicable for the purification of known substances soluble in organic solvents.

It is also possible to isolate nanaomycins A and B from the extracted solution in an acidic condition. In this case, an excessively higher pH should be avoided to obtain a large amount of nanaomycin B, because nanaomycin B may be converted into nanaomycin A in an alkaline condition. For example, an aqueous solution of sodium bicarbonate (1%) is used to elute nanaomycins A and B from the extract with quick speed. Immediately after this, the eluate containing nanaomycins A and B is adjusted to an acidic pH, for example, with hydrochloric acid and further extracted with a suitable organic solvent such as, for example, ethyl acetate or butyl acetate. The thus-obtained extract is concentrated to dryness, resulting in nanaomycins A and B in the form of crude powders which are then subjected to the column chromatography using silica-gel, whereby the crude powders containing nanaomycins A and B are developed with a solvent system of benzene-acetone (4:1 v/v) to elute the fractions containing nanaomycin A, followed by nanaomycin B-containing fractions. The thus-obtained fractions are separately combined and concentrated to dryness. The dried material containing nanaomycin A is dissolved in ethanol which is then added with a small amount of water to give nanaomycin A in the form of needle crystals.

Nanaomycin B can also be purified in a similar manner to that applied to the purification of nanaomycin A, whereby the combined fractions containing nanaomycin B are concentrated to dryness and then subjected to the silica-gel column chromatography using benzene-acetone (3:1 v/v) as the developer.

In the recovery stated above, nanaomycins A and B are eluted from the ethyl acetate layer with 1% of sodium bicarbonate, while nanaomycin C remains in the ethyl acetate layer because nanaomycin B is neutral, which is then concentrated under reduced pressure to dryness to obtain the crude powders of nanaomycin C. The crude powders are chromatographed on a column of silica-gel with chloroform-methanol (50:1 v/v). The fractions containing nanaomycin C are concentrated under reduced pressure to dryness to obtain crude powders of nanaomycin C which are extracted with ethyl acetate and then recrystallized from an ethyl acetate to obtain orange crystals of nanaomycin C.

Nanaomycins A, B and C are assayed in a similar manner to that designated as the paper disc method by Itoh, et al [J. of Antibiotics, 24, 855-859 (1971)], for example as follows:

The strain is cultured at a temperature of 27° C. with shaking. The medium (pH 7.0) contains glycerin (2.0%), soybean meal (2.0%) and NaCl (0.3%). Inhibition zones of a diameter of 17, 27, 28 and 29 mm are observed in the cultured liquor after culturing for 24, 48, 72 and 96 hours, respectively.

Nanaomycin B is easily converted into nanaomycin A in an alkaline condition and is gradually converted in an acidic or neutral condition. For example, nanaomycin A is obtained from nanaomycin B in an alkaline medium in the following manner:

Nanaomycin B (200 mg) is dissolved in 60 ml of 0.1 N sodium hydroxide and the solution is allowed to stand for 10 minutes. After adjusting to pH 2.0 with 6 N hydrochloric acid, the product is extracted with ethyl acetate. The extract is evaporated and orange yellow needles are obtained from an ethanol solution of the product. The compound is identified as nanaomycin A by the melting point, IR spectrum and thin-layer chromatography.

Although nanaomycin B itself exhibits no or little activity, nanaomycin B is converted into nanaomycin A in a culture medium or in living bodies, so that its activity exerts gradually. It is accordingly possible to use both nanaomycins B and A for the same purpose.

The following non-limitative examples illustrate the invention.

EXAMPLE 1

One platinum loop of Streptomyces rosa var. notoensis FERM-P No. 2209 capable of producing nanaomycins was taken from a slant culture and inoculated to a seed medium (pH 7.0) for culturing at a temperature of 27° C. for 2 days. The resultant seed culture was further inoculated to a medium (20 liters) put in a 30-liter jar fermentor at a ratio of 1% and cultured at 27° C. for 4 days with aeration (10 l/min) and agitation (300 r.p.m.). These media contained 2.0% of glycerol, 2.0% of soybean meal and 0.3% of NaCl and had an adjusted pH of 7.0. The media were sterilized at a temperature of 120° C. for 15 minutes before use. After completion of the fermentation, the pH of the cultured broths was 4.8 and an inhibition zone against Mycoplasma gallisepticum (diameter-30 mm) was observed to the supernatant of the broths. The broths (20 liters) were subjected to centrifugation to remove the mycelium. The filtrate was adjusted to a pH of 2.0 with 6 N HCl and was then subjected to extraction with butyl acetate (4 liters). The butyl acetate layer was extracted with 1% sodium bicarbonate aqueous solution (800 ml). The aqueous layer was adjusted to a pH of 2.0 with 6 N HCl and was subjected to extraction with ethyl acetate. The ethyl acetate layer was concentrated and added with petroleum ether to give yellow-brown powders (1.09 g) which were further purified in the following manner.

The crude powders containing nanaomycins A and B were dissolved in ethyl acetate (15 ml) and added with silica-gel (4 g) and then concentrated in vacuo to dryness. The dried material was transferred to a column packed with silica gel (55 g) and then developed with a solvent system of benzene-ethyl acetate (4:1 v/v). The eluate was divided into individual fractions (each 15 ml). Each fraction was then assayed by the above-described paper disc method using Mycoplasma gallisepticum KP-13 as a test microorganism. The first part of the eluate, i.e. Nos. 8 to 22 of the fractions contained nanaomycin A, and No. 14 exhibited a highest activity against the test microorganism. For fractions after No. 30, another solvent system of benzene-ethyl acetate (3:1 v/v) was used as the eluting solution. Nos. 32 to 60 of the divided fractions contained nanomycin B, and the activity of No. 46 was highest against the control microorganism. The fractions Nos. 8 to 22 were combined and concentrated in vacuo to dryness. The dried solid material was dissolved in ethanol and then added with a small amount of water to give yellow needle crystals (31.7 mg). The crystals were recrystallized from an ethanol solution in a similar manner to that described above to give a purified nanaomycin A (25.3 mg; purity: more than 99%; melting point: 178°-180° C.).

UV absorption spectrum of nanaomycin A: λ_(max) ^(MeOH) nm: 250, 274 and 423

IR absorption spectrum of nanaomycin A: Characteristic strong absorptions at 1725, 1640 and 1610 cm⁻¹ when measured by KBr method.

The second part of the fractions (Nos. 32 to 60) was combined and concentrated in vacuo to dryness to give pale yellow powders (450 mg). The powders were further subjected to column chromatography using silica gel in a similar manner to that described above to obtain purified powders of nanaomycin B (270 mg; purity: 99%; melting point: 84°-86° C.).

UV absorption spectrum of nanaomycin B: λ_(max) ^(MeOH) nm: 231 and 352

IR absorption spectrum of nanaomycin B: Characteristic strong absorptions at 1705, 1648 and 1605 cm⁻ when measured by KBr method.

EXAMPLE 2

To the solid material which was obtained by centrifugation of the cultured broths prepared in a similar manner to that described in Example 1, there was added ethyl acetate (5 liters) with agitation. The thus-obtained extract was added with 1% solution of sodium bicarbonate (2 liters) to transfer the material including nanaomycin A and B to the aqueous layer. The aqueous layer was adjusted to a pH of 2.0 with hydrochloric acid and was then subjected to extraction with ethyl acetate (500 ml). The extracted solution was concentrated in vacuo to dryness to give crude powders (521 mg) in yellow brown. The powders were subjected to silica gel column chromatography and the eluate was treated to obtain nanaomycins A and B in a similar manner to that described in Example 1.

    ______________________________________                                                   Yield   Melting Point                                                                               Purity                                          ______________________________________                                         Nanaomycin A                                                                               13 mg     173-175° C.                                                                          95%                                         Nanaomycin B                                                                               85 mg     82-84° C.                                                                            92%                                         ______________________________________                                     

What is claimed is:
 1. A new compound nanaomycin B represented by general formula: ##STR4##
 2. A therapeutic composition comprising an effective amount of the compound of claim 1 as an active ingredient. 